The resulting altitude is not just taken from baro sensor, it is
calculated from the vertical acceleration between the baro measurments.
So what would i looked here at is a calculated altitude/clean baro values
comparison. If their behaviour dont match, the problem is in acc
measurments.
As I already mentioned, the resulting altitude estimation is very
sensitive to the vibration level.
Did you try all the different boards on the same copter frame with the
same mounting?